In the development of combustion engines for motor-driven tools, such as chainsaws, hedge trimmers, grass trimmers etc., bearing sleeves have been used to eliminate the need for after-treatment of bearing seats of crankshaft bearings after the bearings seats have been manufactured.
In U.S. Pat. No. 4,974,973 and WO97/45649, crankshaft bearing arrangements have been described using such bearing sleeves. In the bearing arrangement of, for example, U.S. Pat. No. 4,974,973, a bearing can be arranged in a bearing sleeve, which is formed as a tin cup with a rubber coated outer periphery. The rubber coated outer periphery is arranged to compensate for tolerances, e.g. size variations in the production of bearing seats and to seal against the cylinder and the crankcase. Also, the arrangement has an internal periphery provided with a sealing ring to seal against the crankshaft.
Even if such arrangements have a lot of advantages, some exemplary problems may occur as follows:                Due to the rather large tolerances in such an arrangement, there is a risk that the bearing is either too loosely arranged in the sleeve, with a result that the bearing may rotate in the bearing sleeve or that the bearing including the bearing sleeve will rotate in the bearing seat, or that the bearing will press too hard in the sleeve, risking obliqueness of the bearing or that the bearing and/or the bearing sleeve is squeezed in the bearing seat such that the bearing and/or the bearing sleeve finally breaks.        Even if dimensions are achieved for which a proper squeezing of the bearing and the bearing sleeve is achieved, it may be difficult to seal such an arrangement. As a result, it may be necessary to seal during operation with a substantial amount of silicone glue between the bearing seat and bearing sleeve.        
Also, such a solution is rather expensive to produce, since an expensive kind of rubber is usually used for the rubber-coated outer periphery.